Micro Benchmarks for HashMap vs Array

Test.java

import java.util.*;
import java.util.concurrent.*;

public class Test {
    public static void main(String[] args) {

        ConcurrentHashMap<Integer, Long> map;
        long[] array_key;
        long[] array_value;
        long avgHashMapTime;
        long avgArrayTime;

        map = new ConcurrentHashMap<Integer, Long>();

        long start = System.nanoTime();
        for (int i = 0; i < 1_000_000; i++) {
            map.put(i, 1234L);
        }
        long end = System.nanoTime();
        avgHashMapTime = end - start;


        array_key = new long[1_000_000];
        array_value = new long[1_000_000];

        long start_array = System.nanoTime();
        for (int i = 0; i < 1_000_000; i++) {
            array_key[i] = i;
            array_value[i] = i;
        }
        long end_array = System.nanoTime();
        avgArrayTime = end_array - start_array;

        System.out.format("HashMap Insert time:\t %20d\n", avgHashMapTime);
        System.out.format("Array Insert time:\t %20d\n", avgArrayTime);

        start = System.nanoTime();
        for (int i = 0; i < 1_000_000; i++) {
            long x = map.get(i);
        }
        end = System.nanoTime();
        System.out.format("HashMap Get time:\t %20d\n", end - start);

        start_array = System.nanoTime();
        for (int i = 0; i < 1_000_000; i++) {
            long x = array_value[i];
            long y = array_key[i];
        }
        end_array = System.nanoTime();
        System.out.format("Array Get time:\t \t %20d\n", end_array - start_array);
    }
}